Multicenter‐Bond‐Based Quantum Interference in Charge Transport Through Single‐Molecule Carborane Junctions

Abstract

Molecular components are vital to introduce and manipulate quantum interference (QI) in charge transport through molecular electronic devices.Uptonow,the functional molecular units that show QI are mostly found in conventional p-a nd s-bond-based systems;i ti st hus intriguing to study QI in multicenter bonding systems without both p-a nd sconjugations.N ow the presence of QI in multicenter-bondbased systems is demonstrated for the first time,t hrough the single-molecule conductance investigation of carborane junctions.W ef ind that all the three connectivities in carborane frameworks showdifferent levels of destructive QI, which leads to highly suppressed single-molecule conductance in para-and meta-connected carboranes.T he investigation of QI into carboranes provides ap romising platform to fabricate molecular electronic devices based on multicenter bonds.Quantum interference (QI) offers the unique opportunity to tune charge transport through molecular devices and materials, [1] which leads to various applications such as QIbased thermoelectrics, [2] molecular memory, [3] molecular transistors, [4] and sensors. [5] Them olecular building blocks play avital role in investigating QI-based molecular junctions. Up to now,the molecular building blocks with QI are mostly found in conventional two-center-two-electron (2c-2e) bondbased systems,w hich lead to p-interference [1d, 3, 4, 6] and sinterference. [2b] In the p systems,the involvement of s bonds are inevitable,a nd the p-interference can only suppress the p channels,l eaving the s channels unaffected. When the molecular building blocks are only constructed from s bonds with the vanishing of p channels,t he s-interference will lead to strong conductance suppression, as recently demonstrated in s-conjugated silane system. [2b] Besides the 2c-2e bondbased system, inorganic clusters based on metal-metal bonds were also found to show QI. [7] These progresses suggest the great potential of exploring QI in distinctive bonding systems.Besides the conventional 2c-2e bonds,t here exist abundantly unconventional multicenter bonding systems,showing much richer patterns to form bonds with the absence of both p and s conjugations (Figure 1a). Thus,whether and how QI is present in those multicenter bonding systems become an unexplored and promising avenue.T oe xplore such multicenter-bond-based QI, carborane is an ideal molecular building block. Since the carborane framework is constructed from three-center-two-electron( 3c-2e) bonds,t he electrons of the 3c-2e bonds can delocalize around the framework, ensuring efficient conjugation between each multicenter bond. Thee fficient conjugation of carborane leads to distinctively three-dimensional aromaticity [8] and high stability, [9] which has already been applied in ab road spectrum of fields, [9b,10] such as catalysis, [11] supramolecular chemistry, [12] and optoelectronics. [13] Thus the single-molecule conductance investigation of carborane provides an ideal testbed to investigate the multicenter-bond-based QI, which w...

Identifying the Conformational Isomers of Single-Molecule Cyclohexane at Room Temperature

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“…Flicker noise analysis is performed according to previous results. 27,31,61 We suspended the retracting process of the tip for 150 ms from collecting about 10,000 of such traces and getting the noise spectrum by fast Fourier transform. The noise power is calculated by the noise spectrum integration from 100 to 1,000 Hz, which is plotted against the average conductance.…”

Single-molecule switching via controlled tautomerization at room temperature

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